audio: Clean up and fix the bluetooth HAL module

Fix the issue with retrieving BluetoothA2dp and BluetoothLe
instances access.

In 'Module::connectExternalDevice', always call
'populateConnectedDevicePort' to allow the module implementation
to cancel device connection.

Move frame count calculation into Utils.
Clean up includes and 'using' directives.

Bug: 302132812
Test: atest VtsHalAudioCoreTargetTest
Change-Id: I22f65b8bcdcdd9bcd67a8290520eb4a465d4c720